fix(cli): spell date and sequence strategies as configured in JSON output

[BryanFRD]

Closes #1292

strategy_label (which feeds bump_type in check --json and release --json) and the strategy field of why --json built the name from Debug lowercased, so a calver-short-seq package reported calvershortseq, a value the config rejects. Both now use VersioningStrategy's Display from #1259, so they print calver-short, calver-seq and calver-short-seq.

This changes JSON values that scripts may match on, which is why #1259 left it out. It ships as a fix, not a major: the old spelling was never valid configuration and no documentation listed it. calver, sequential, the semver bump types and FERRFLOW_BUMP_TYPE (which comes from BumpType, not this label) are unchanged.

A new test pins strategy_label for a hyphenated strategy, a semver bump and a forced version.

[ferrfleet]

Looks correct. VersioningStrategy's Display impl already matches the serde kebab-case spelling (strategy_display_matches_the_config_spelling checks it), so to_string() fixes calvershortseq -> calver-short-seq in both places. The new test covers the date/seq, semver and forced branches.

Nit: the other format!("{x:?}").to_lowercase() calls in api_check.rs and plan_interactive.rs use BumpType, which has single-word variants and its own Display. They aren't wrong, but to_string() would be more consistent there too.